1. Field of the Invention
This invention relates to apparatus for detecting the shape of a strip being rolled. More particularly, it relates to apparatus wherein a plurality of rings disposed in the direction of the width of a strip are pressed against the strip so as to detect the flatness of the strip in the direction of the width.
2. Description of the Prior Art
In the cold rolling, the flatness of a strip is an important matter of interest. As the final product of the rolled strip is thinner, the control of the flatness of the strip or the shape control is a more serious problem to be solved.
As regards an uneven rolled strip under the state under which no tension is exerted, the unevenness of the strip can be easily found by sight. However, under the state under which a tension acts on a strip as in course of rolling, the unevenness of the strip is stretched and cannot be visually found. Accordingly, there have heretofore been developed various shape detectors which detect the shape of a strip continuously in the state in which the strip is subjected to a tension and in which it is running.
As an example, a shape detector has been known in which a plurality of rings disposed along the width of a strip are pressed against the strip, the components of the tension of the strip as act on the respective rings are measured, and the shape of the strip is detected from the tensile distribution state of the strip in the direction of the width thereof.
This shape detector is based on the principle that, in the tensioned state, the shape or unevenness of the strip appears as non-uniformity in the distribution of the tensile components of the strip in the direction of the width of the strip, so the shape can be detected by measuring the tensile distribution.
As a typical example of the shape detector of such a type having the allocated rings, there is one wherein a plurality of rings are rotatably fitted on a shaft transverse to a strip through roller bearings and wherein the components of the tension of the strip as act on the respective rings are detected by load cells disposed between the roller bearing and the shaft (refer to, for example, U.S. Pat. No. 3,902,363). This shape detector, however, requires the roller bearing on the inner periphery of each ring in order to ensure a smooth rotation between the ring and the shaft. In general, the roller bearing has a play of several tens to several hundreds microns however precisely it is fabricated. On the other hand, a flatness of several tens microns is required for the shape of the strip. Accordingly, even when the tensile components are measured with the load cells of high precision, essentially the shape of the strip is not assessed on account of the play of the roller bearing.
Further, the surface of the ring held in contact with the strip throughout undergoes abrasion due to its friction with the strip or flaws due to the flaws or fine uneven parts of the surface of the strip, and it needs to be polished frequently. Since, however, the roller bearing is contained on the inner periphery of the ring as stated previously, the ring surface will be eccentrically polished on account of the play of the roller bearing if it is polished by rotating the ring as fitted on the shaft.
Further, the plurality of load cells are disposed inside each ring. Since the load cell requires a load detecting capability of high precision, it needs a favorable atmosphere of measurement and is very expensive, and besides, it is less immune to an impact load. Notwithstanding that a routine insepection is accordingly necessary, the overhaul of the load cell is troublesome as it is assembled inside the ring.
On the other hand, there has been developed a shape detector which employs neither load cells nor roller bearings and in which a pressurized fluid is caused to flow between a shaft and rings so as to ensure the smooth rotation between the shaft and the rings by means of a fluid film formed of the fluid, while on the basis of the fact that the fluid pressures between the respective rings and the shaft are proportional to tensile components, the fluid pressures are detected so as to effect the shape detection (U.S. Pat. No. 3,499,306).
Also in this detector, however, means for sensing the pressures of the fluid need to be contained in the shaft. Moreover, the fluid is spouted towards the rings from fine nozzles provided in the shaft, and hence, such care as removal of dust in the fluid must be taken into consideration.
The most desirable shape detector is one which, of course, has a high capability of detecting a shape, in which a play occurring in a rotary part is little, which does not employ expensive load cells, and which does not include load cells requiring maintenance therein and is simple in overhaul and maintenance.